18:20Doctor Who (1963–1996)Season 13Terror of the Zygons: Part 4BBC One Duration: 25 minutes Audio described Signed Sat 20th Sep 1975, 18:20 on BBC One OxfordshireAvailable for 21 daysWatch nowBroton the Zygon warlord, disguised as the Duke of Forgill, intends to use the Skarasen to attack the World Energy Conference in London.GenresDramaSciFi & FantasyBrandDoctor Who (1963–1996)SeriesDoctor Who (1963–1996): Season 13 Source: BBC Online